/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *  http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mlizhi.base.codec.net;

import java.io.ByteArrayOutputStream;
import java.io.UnsupportedEncodingException;
import java.util.BitSet;

import com.mlizhi.base.codec.BinaryDecoder;
import com.mlizhi.base.codec.BinaryEncoder;
import com.mlizhi.base.codec.CharEncoding;
import com.mlizhi.base.codec.DecoderException;
import com.mlizhi.base.codec.EncoderException;
import com.mlizhi.base.codec.StringDecoder;
import com.mlizhi.base.codec.StringEncoder;
import com.mlizhi.base.codec.binary.StringUtils;


/**
 * <p>
 * Codec for the Quoted-Printable section of <a href="http://www.ietf.org/rfc/rfc1521.txt">RFC 1521 </a>.
 * </p>
 * <p>
 * The Quoted-Printable encoding is intended to represent data that largely consists of octets that correspond to
 * printable characters in the ASCII character set. It encodes the data in such a way that the resulting octets are
 * unlikely to be modified by mail transport. If the data being encoded are mostly ASCII text, the encoded form of the
 * data remains largely recognizable by humans. A body which is entirely ASCII may also be encoded in Quoted-Printable
 * to ensure the integrity of the data should the message pass through a character- translating, and/or line-wrapping
 * gateway.
 * </p>
 * 
 * <p>
 * Note:
 * </p>
 * <p>
 * Rules #3, #4, and #5 of the quoted-printable spec are not implemented yet because the complete quoted-printable spec
 * does not lend itself well into the byte[] oriented codec framework. Complete the codec once the steamable codec
 * framework is ready. The motivation behind providing the codec in a partial form is that it can already come in handy
 * for those applications that do not require quoted-printable line formatting (rules #3, #4, #5), for instance Q codec.
 * </p>
 * 
 * @see <a href="http://www.ietf.org/rfc/rfc1521.txt"> RFC 1521 MIME (Multipurpose Internet Mail Extensions) Part One:
 *  Mechanisms for Specifying and Describing the Format of Internet Message Bodies </a>
 * 
 * @author Apache Software Foundation
 * @since 1.3
 * @version $Id: QuotedPrintableCodec.java 798333 2009-07-27 23:41:58Z ggregory $
 */
public class QuotedPrintableCodec implements BinaryEncoder, BinaryDecoder, StringEncoder, StringDecoder {
/**
 * The default charset used for string decoding and encoding.
 */
private final String charset;

/**
 * BitSet of printable characters as defined in RFC 1521.
 */
private static final BitSet PRINTABLE_CHARS = new BitSet(256);

private static final byte ESCAPE_CHAR = '=';

private static final byte TAB = 9;

private static final byte SPACE = 32;
// Static initializer for printable chars collection
static {
// alpha characters
for (int i = 33; i <= 60; i++) {
PRINTABLE_CHARS.set(i);
}
for (int i = 62; i <= 126; i++) {
PRINTABLE_CHARS.set(i);
}
PRINTABLE_CHARS.set(TAB);
PRINTABLE_CHARS.set(SPACE);
}

/**
 * Default constructor.
 */
public QuotedPrintableCodec() {
this(CharEncoding.UTF_8);
}

/**
 * Constructor which allows for the selection of a default charset
 * 
 * @param charset
 *  the default string charset to use.
 */
public QuotedPrintableCodec(String charset) {
super();
this.charset = charset;
}

/**
 * Encodes byte into its quoted-printable representation.
 * 
 * @param b
 *  byte to encode
 * @param buffer
 *  the buffer to write to
 */
private static final void encodeQuotedPrintable(int b, ByteArrayOutputStream buffer) {
buffer.write(ESCAPE_CHAR);
char hex1 = Character.toUpperCase(Character.forDigit((b >> 4) & 0xF, 16));
char hex2 = Character.toUpperCase(Character.forDigit(b & 0xF, 16));
buffer.write(hex1);
buffer.write(hex2);
}

/**
 * Encodes an array of bytes into an array of quoted-printable 7-bit characters. Unsafe characters are escaped.
 * 
 * <p>
 * This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
 * RFC 1521 and is suitable for encoding binary data and unformatted text.
 * </p>
 * 
 * @param printable
 *  bitset of characters deemed quoted-printable
 * @param bytes
 *  array of bytes to be encoded
 * @return array of bytes containing quoted-printable data
 */
public static final byte[] encodeQuotedPrintable(BitSet printable, byte[] bytes) {
if (bytes == null) {
return null;
}
if (printable == null) {
printable = PRINTABLE_CHARS;
}
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
for (int i = 0; i < bytes.length; i++) {
int b = bytes[i];
if (b < 0) {
b = 256 + b;
}
if (printable.get(b)) {
buffer.write(b);
} else {
encodeQuotedPrintable(b, buffer);
}
}
return buffer.toByteArray();
}

/**
 * Decodes an array quoted-printable characters into an array of original bytes. Escaped characters are converted
 * back to their original representation.
 * 
 * <p>
 * This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
 * RFC 1521.
 * </p>
 * 
 * @param bytes
 *  array of quoted-printable characters
 * @return array of original bytes
 * @throws DecoderException
 *  Thrown if quoted-printable decoding is unsuccessful
 */
public static final byte[] decodeQuotedPrintable(byte[] bytes) throws DecoderException {
if (bytes == null) {
return null;
}
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
for (int i = 0; i < bytes.length; i++) {
int b = bytes[i];
if (b == ESCAPE_CHAR) {
try {
int u = Utils.digit16(bytes[++i]);
int l = Utils.digit16(bytes[++i]);
buffer.write((char) ((u << 4) + l));
} catch (ArrayIndexOutOfBoundsException e) {
throw new DecoderException("Invalid quoted-printable encoding", e);
}
} else {
buffer.write(b);
}
}
return buffer.toByteArray();
}

/**
 * Encodes an array of bytes into an array of quoted-printable 7-bit characters. Unsafe characters are escaped.
 * 
 * <p>
 * This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
 * RFC 1521 and is suitable for encoding binary data and unformatted text.
 * </p>
 * 
 * @param bytes
 *  array of bytes to be encoded
 * @return array of bytes containing quoted-printable data
 */
public byte[] encode(byte[] bytes) {
return encodeQuotedPrintable(PRINTABLE_CHARS, bytes);
}

/**
 * Decodes an array of quoted-printable characters into an array of original bytes. Escaped characters are converted
 * back to their original representation.
 * 
 * <p>
 * This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
 * RFC 1521.
 * </p>
 * 
 * @param bytes
 *  array of quoted-printable characters
 * @return array of original bytes
 * @throws DecoderException
 *  Thrown if quoted-printable decoding is unsuccessful
 */
public byte[] decode(byte[] bytes) throws DecoderException {
return decodeQuotedPrintable(bytes);
}

/**
 * Encodes a string into its quoted-printable form using the default string charset. Unsafe characters are escaped.
 * 
 * <p>
 * This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
 * RFC 1521 and is suitable for encoding binary data.
 * </p>
 * 
 * @param pString
 *  string to convert to quoted-printable form
 * @return quoted-printable string
 * 
 * @throws EncoderException
 *  Thrown if quoted-printable encoding is unsuccessful
 * 
 * @see #getDefaultCharset()
 */
public String encode(String pString) throws EncoderException {
if (pString == null) {
return null;
}
try {
return encode(pString, getDefaultCharset());
} catch (UnsupportedEncodingException e) {
throw new EncoderException(e.getMessage(), e);
}
}

/**
 * Decodes a quoted-printable string into its original form using the specified string charset. Escaped characters
 * are converted back to their original representation.
 * 
 * @param pString
 *  quoted-printable string to convert into its original form
 * @param charset
 *  the original string charset
 * @return original string
 * @throws DecoderException
 *  Thrown if quoted-printable decoding is unsuccessful
 * @throws java.io.UnsupportedEncodingException
 *  Thrown if charset is not supported
 */
public String decode(String pString, String charset) throws DecoderException, UnsupportedEncodingException {
if (pString == null) {
return null;
}
return new String(decode(StringUtils.getBytesUsAscii(pString)), charset);
}

/**
 * Decodes a quoted-printable string into its original form using the default string charset. Escaped characters are
 * converted back to their original representation.
 * 
 * @param pString
 *  quoted-printable string to convert into its original form
 * @return original string
 * @throws DecoderException
 *  Thrown if quoted-printable decoding is unsuccessful.
 *  Thrown if charset is not supported.
 * @see #getDefaultCharset()
 */
public String decode(String pString) throws DecoderException {
if (pString == null) {
return null;
}
try {
return decode(pString, getDefaultCharset());
} catch (UnsupportedEncodingException e) {
throw new DecoderException(e.getMessage(), e);
}
}

/**
 * Encodes an object into its quoted-printable safe form. Unsafe characters are escaped.
 * 
 * @param pObject
 *  string to convert to a quoted-printable form
 * @return quoted-printable object
 * @throws EncoderException
 *  Thrown if quoted-printable encoding is not applicable to objects of this type or if encoding is
 *  unsuccessful
 */
public Object encode(Object pObject) throws EncoderException {
if (pObject == null) {
return null;
} else if (pObject instanceof byte[]) {
return encode((byte[]) pObject);
} else if (pObject instanceof String) {
return encode((String) pObject);
} else {
throw new EncoderException("Objects of type " + 
  pObject.getClass().getName() + 
  " cannot be quoted-printable encoded");
}
}

/**
 * Decodes a quoted-printable object into its original form. Escaped characters are converted back to their original
 * representation.
 * 
 * @param pObject
 *  quoted-printable object to convert into its original form
 * @return original object
 * @throws DecoderException
 *  Thrown if the argument is not a <code>String</code> or <code>byte[]</code>. Thrown if a failure condition is
 *  encountered during the decode process.
 */
public Object decode(Object pObject) throws DecoderException {
if (pObject == null) {
return null;
} else if (pObject instanceof byte[]) {
return decode((byte[]) pObject);
} else if (pObject instanceof String) {
return decode((String) pObject);
} else {
throw new DecoderException("Objects of type " + 
  pObject.getClass().getName() + 
  " cannot be quoted-printable decoded");
}
}

/**
 * Returns the default charset used for string decoding and encoding.
 * 
 * @return the default string charset.
 */
public String getDefaultCharset() {
return this.charset;
}

/**
 * Encodes a string into its quoted-printable form using the specified charset. Unsafe characters are escaped.
 * 
 * <p>
 * This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
 * RFC 1521 and is suitable for encoding binary data and unformatted text.
 * </p>
 * 
 * @param pString
 *  string to convert to quoted-printable form
 * @param charset
 *  the charset for pString
 * @return quoted-printable string
 * 
 * @throws java.io.UnsupportedEncodingException
 *  Thrown if the charset is not supported
 */
public String encode(String pString, String charset) throws UnsupportedEncodingException {
if (pString == null) {
return null;
}
return StringUtils.newStringUsAscii(encode(pString.getBytes(charset)));
}
}
